A Little Christmas Surprise
by Lur27
Summary: Sequel to "An Unexpected Little Surprise". Can be read without reading the first one if you check the AN. Aidan finds out about Kate's little secret. Will it be a happy Christmas after Castle finds out?
1. Chapter 1

**A/N:** Happy holidays, guys! I know I've been MIA for a long time, but I got inspired a few days ago, and even though this will probably be finished by the end of the Christmas holidays, I wanted to post it anyway. Always late... Meh.

This could be labeled as some kind of sequel to my story "An Unexpected Little Surprise", which was finished a couple of years ago, but I think anybody could read it if they know these few things:

*On my previous story Castle found out he had a secret child with a one night stand who gets murdered.

*After taking paternity tests and going through all the procedures he got the custody of the boy.

*The kid is super attached to Kate since the beginning.

I think that should help the ones who haven't read the first part to understand what's going on on this one. I hope you guys enjoy it.

Please, let me know what you think.

* * *

><p><span><strong>Chapter 1<strong>

The sun picked through the half-open blinds, tickling Kate's nose and making her eyes flutter. If only she could stay in bed and skip work for just one day. She kept finding herself wishing that same thing more and more often lately. Maybe the season had something to do with it. Christmas was not exactly her favorite time of the year. Even now, that she had a family to celebrate it with, it still made her feel all melancholic and blue.

She turned around in bed, stretching her limbs as far as she could and expecting to find her sleeping fiancé snoring softly by her side, but when she opened her eyes, she was faced instead with a set of tiny feet stuffed into fluffy Rudolf the Reindeer socks that were almost coming off from twisting and turning all night long.

Kate sighed and ran a hand along one of the chubby, little legs that were coming out from underneath the comforter. It was the third time Aidan joined them in bed that week.

Normally, when that happened, one or both of them would notice the kid coming into the bedroom, and after comforting him or even letting him fall back asleep on their bed, Castle - most times, since Kate would fall asleep with Aidan curled at her side - would pick him up and take him back to his own bed. But lately, the little rascal had developed ninja skills and none of them was able to notice when he entered the room or even got into bed with them, just finding out they had a little visitor once they woke up in the morning.

She smiled softly at the view her two boys made. Castle sprawled face down on his side of the bed, both arms framing his head on the pillow, his hair sleep-tousled and spiking in every possible direction. Aidan right in between the writer and her, laying upside down, his body hidden under the covers, with just his socked, little feet peeping out.

Turning the covers down, she fished Aidan from underneath them and flipped him, placing him on her side of the bed and covering him with the comforter again. It was a real blessing that he had his father's ability to sleep like a rock and be dead to the world once he fell under Morpheus spell.

With a last longing glance towards the bed, she picked her clothes for the day and padded her way to the bathroom stifling a yawn.

* * *

><p>When she came out of the en-suit, all clean and ready to roll, Aidan was already awake and waiting for her patiently, sitting crossed legged on her side of the bed, his hands playing absentmindedly with a loose thread on the sheets.<p>

The boy's face lit up when he saw her and he smiled a huge toothy grin before crawling his way to the end of the bed, jumping down easily and taking the hand she was offering him to lead him to the kitchen.

Kate helped him climb on a stool and placed a kiss to the top of his head, ruffling his already too long hair. They really needed to take him to get a haircut, and soon.

She opened the fridge and took out a bowl with fresh fruit and placed it on the kitchen island, right at Aidan's reach, so the boy could eat some while she worked on their breakfast.

After getting the coffee maker started and putting some toast in the toaster, she turned around, a raised eyebrow and a smirk on her face, causing the kid to stop chewing on the strawberry he was eating and smile at her sheepishly, full mouth and all.

"So. What happened last night, munchkin?" She asked amused. "Was it monsters under your bed or aliens from outer space knocking on your window?"

Aidan chuckled at that and squinted in thought. "Um… I think it was the aliens." He said with a very serious expression. "They're scary."

"Oh, I bet." Kate replied, picking up two pieces of toast and putting them on a plate that she served to Aidan with a glass of chocolate milk. "But if you were so scared, how is it that you didn't wake us up? Daddy could have gone to your bedroom and scare the aliens away, you know."

The boy frowned and shook his head, giving her an outraged look. "No, Katie! Daddy's powers don't work with aliens."

"Oh, I see. And what about mine? Would mine have worked on them?" She asked amused, knowing that Aidan pretty much thought she was some kind of superhero.

"Uh uh." The boy replied, a piece of toast in his mouth and a chocolate milk moustache adorning his upper lip. "They are not afraid of cops. They have laser guns, Katie. Those are worse than bullets. They can disintegrate you." He explained solemnly. "Don't you remember 'Mars Attacks'?"

Kate's eyebrows raised in surprise at that. "When in the world have you watched 'Mars Attacks'? That is not a children's movie, bug."

Aidan shrugged and scrunched his nose in an adorable way that reminded Kate of the boy's father, knowing he had just given away some secret information. "I watched with daddy a few weeks ago. He said it was fun, but it was scary." He mumbled against the rim of his glass. "Do you think aliens are gonna come and kill us all?"

His eyes were big and uncertain and Kate's heart hurt a little at the little boy's trepidation. The poor thing… She would have to have a long talk with her fiancé about what was appropriate to let an impressionable almost 5 year old watch and what was not.

She reached for Aidan's hand and squeezed it in her own, moving closer to him over the kitchen island. "No, baby. I am sure we're safe." She reassured him. "What you watched with your daddy was just a movie. It was not real, you know that, right?"

"Uh huh."

"Ok, then."

She cleared up the breakfast bar and picked the boy up in her arms, hugging him hard. "If you get scared at night you have to wake us up, ok, bug? If you don't do it we can't know that you're scared and won't be able to help you."

"Okay." He breathed against her neck. "I'm sorry."

"No need to be, sweetie." She said, pressing a soft kiss to the boy's forehead. "Now let's go wake up your old man. You guys should be getting ready for your last day of pre-school of the year."

* * *

><p>It was around 2:30 pm when Castle arrived at the door of Miller Preschool to pick up Aidan, after a long and productive morning.<p>

After leaving his son at school, he had been able to finish three chapters of the new Nikki Heat novel and even had time to go grocery shopping, saving Beckett the inconvenience of having to go with them after work. Shopping with two grabby hands coming out of the cart, trying to pick up all the stuff in the candy isle was not exactly easy and it drove his fiancée a little insane.

He waited for a few minutes, sharing tight smiles and nods with other parents, until the doors opened and a couple of lines of children preceded by their teachers came out of the building; the kids giggling and screaming, happy to be going home to their families and start the so awaited Christmas break.

Short seconds later he was hit by a tiny body who attached to his leg and looked up at him with his same blue eyes.

"Hi daddy! I missed you." The boy chirped. "Are we picking Katie up at the precinct?"

Castle laughed and crouched to be at the boy's height, ruffling his hair and softly pinching his cheek. "Yeah, buddy. We are. But first we're going to have some fun at the park, ok? And I missed you too, by the way." Aidan gave him a huge smile and stepped closer to hug him tight, which gave Rick the chance to pick him up and put him on his shoulders. "Hold tight, champ, we have a long walk ahead."

* * *

><p>They arrived at the precinct by 4:30. It was a little early, but he knew when Kate saw they were there, she would try to get them out as soon as possible. She didn't like the idea of Aidan being surrounded by criminals and crime scene pictures hanging off the murder boards.<p>

Whenever he stepped into the bullpen with the kid, Kate gave him a reproving look and they had the same talk once they got home about how he used this as a tactic to make her leave earlier.

He secretly thought that having her home early, even if it was by just 10 minutes, was worth suffering the "Beckett wrath".

As soon as they came out of the elevator the boy spotted Ryan, who was at his desk talking on the phone, and ran to him calling "Uncle Ry! School is over!"

The cop hung up the phone and looked up surprised by the kid's pitched voice smiling widely when he saw him running towards his desk.

"Hey, bud! That is awesome!" He replied to the cheery boy. Then looked up at Castle and shook his head at him, a somber grin pulling his lips upwards. "Beckett is gonna kill you, man."

Castle shrugged and gave his friend an unconcerned smirk. "Where is she, by the way?"

Esposito came out of the conference room carrying a big brown box with him and placed it on his desk. "She disappeared a while ago into the break room. She was on the phone with someone." The detective informed him, before high fiving Aidan and going back to his job.

"Ok, bug. Why don't you go find, Kate, huh? The sooner she knows we're here, the sooner we'll be going home."

* * *

><p>She had been waiting for Lanie's call for about two days, when she visited her friend to ask her a huge favor, but right now, listening to what the ME was telling her, she would have rather not heard from her at all.<p>

"I can't be pregnant, Lanie. Are you absolutely, 100% sure?" She questioned her friend for the thousandth time, her voice quivering.

Lanie sighed. "Yes, Kate. I am 100% sure. I did a blood test, remember? Three times. No chance for a mistake. You and writer boy are having a baby."

"Shit!" Kate mumbled, rubbing her forehead insistently, trying to come to terms with the new developments in her life. "This is… This is not good."

"Why? Kate, I know you're planning your wedding, but you already have a kid. What would be so wrong about having another? You told me you wanted to have kids with Castle not long ago." Lanie was trying to be the voice of reason here, but her friend was freaking out so much, that it was becoming an impossible mission.

"And I do. I want to have a baby with him, but this is not the best time… Aidan… He's not even 5 yet and he's so needy, Lanie. I can't divide my time between two kids. Hell, I can barely divide my time between work and home. How am I going to do this?"

The ME snapped her tongue and let out a deep breath. "The same way you did it when that boy burst into your lives over a year ago. You just do it, Kate." She reminded her. "You are a wonderful mom for that kid, and you will be a wonderful mom for this one. Stop second guessing yourself."

Kate groaned. "This is not the same, Lanie. Aidan was already three when we got him. I… I've never been responsible of a baby for more than an evening when I was a teen. To be honest, 3 am feedings and diaper changes don't sound very appealing right now."

"Neither does sharing your bed with a four years old, or staying up with him until the wee hours in the morning because he's having nightmares, but you do it, Kate. And you don't mind one bit because you love that kid." Lanie offered, trying to make her friend see that she was going crazy about nothing.

Kate sighed loudly and ran her fingers through her already tousled hair. "I know. It's just… Do you think it will be different? I mean, this child being Castle's and mine… Should I worry about Aidan? He's so attached to me, and he keeps worrying about me not being his mom. It's like he expects me to walk away someday and if we have a new baby in the house… I don't think he is ready for that and the last thing I need right now is having to deal with a jealous kid."

Aidan listened to Kate from his hiding place behind the door. He had been waiting for her to come out so he could scare her like he did at home all the time, but after listening to her talking on the phone, he felt his little heart sink.

She didn't want to deal with a jealous kid, and he was that kid.

His daddy and Katie were going to have a new baby. He had no idea how that worked, but apparently, parents didn't have much of a say about when they had their babies, and that meant he was becoming a nuisance; at least to his father's fiancée.

The tears started forming in his bright blue eyes, but he kept them at bay. He had to come out to the bullpen again, and he didn't want his dad to know what happened.

* * *

><p>When he came out Castle was waiting for him sitting on his chair that still remained unmoved beside Beckett's desk, even though he didn't get to sit on it very often anymore.<p>

"Hey, buddy. Did you find Kate?" Castle asked, brows furrowing at the kid's pouty face.

The boy just nodded and ran to Ryan, who was talking on the phone again, but picked him up and sat him on his lap, ruffling his hair.

Not two minutes later, Kate came out of the break room to find her two boys waiting for her in the bullpen. She smiled to Castle and signaled him to stay quiet as she walked towards Ryan and Aidan, who were playing some silly game on the cop's computer.

The boy loved to scare her by coming upon her from his favorite hiding places, or even startling her when she was reading and wasn't expecting anybody around. Most of the times she knew he was there, but pretended to be scared to the boy's delight. Every time she did it to him, the kid squealed and laughed hysterically, so now it had become a thing between the two of them. She loved making him laugh.

Kate approached them carefully; trying to minimize the sound of her heals against the wooden floor of the bullpen. The two boys were completely absorbed by the game and didn't notice her presence as she stood behind Ryan. She put her hands over Ryan's shoulders and then shook him hard, yelling, "I gotcha, bug! And you too, _detective_ Ryan."

Both, the man and the kid, screamed loudly, Ryan rubbing a hand down his face and glaring at her and Esposito who was laughing so hard he could barely breathe.

"Jesus, Beckett! You almost gave me a heart attack!" The man choked out.

She laughed and moved to the side to check on Aidan, but the boy turned his attention to the game immediately, not giving her a single look or even a hello.

Kate's face fell and she felt a pang in her chest and her eyes stinging a bit. Aidan had _never_ done that, but she thought that kids could act in weird ways sometimes, so she decided to give him some time and wait until he came to her. Because he would, right?

Still a little confused, she made her path back to her desk and Castle, who was furiously typing on his phone and seemed completely oblivious to what had occurred a few feet away from him.

Kate sank into her chair completely deflated and poked Castle to get his attention. "Is there anything wrong with the bug?" She inquired concerned.

Castle frowned and looked at the boy playing happily with Ryan. "Uh… not that I know of. Why?"

"He completely ignored me just now. He didn't even look at me, Castle."

The writer's frown became even deeper and he reached for her hand that was lying on her desk, nervously scratching a crease on the wood. "Hm. That's weird. But now that you say that… He went to look for you at the break room, but he came back a few minutes later looking as if he had seen a ghost."

Kate groaned. "Ugh, Castle. I've told you a million times that this is no place for a kid. What if he saw anything that scared him? He's already having nightmares almost every night. The last thing he needs is to get spooked by some creepy picture he sees hanging around here." She scolded him. "And we will talk about letting him watch 'Mars Attacks' with you the other day."

Castle swallowed the big lump in his throat and nodded, knowing there was no way he could get out of this one. "I'm sorry?"

* * *

><p>After clearing her desk and turning off her computer, they said goodnight to the boys and headed out of the precinct and into the freezing New York evening.<p>

Castle's arm was around Kate's shoulders and his other hand held Aidan's, who was strangely quiet.

Kate had started to get anxious about the little boy's behavior, so she squeezed her boyfriend's hand and removed his arm from around her with a reassuring smile before moving to his other side and touching Aidan's head softly, smiling sweetly at the boy when he looked up at her.

"Hey, munchkin. You're very quiet today." She addressed. "And you haven't even given me a hug yet."

She tried to keep all the anxiety and worry to herself, smiling softly, but Aidan just looked at her with his big, blue eyes and a neutral expression on his face.

Kate made Castle stop, putting a hand on his shoulder, and crouched before the kid. "Is everything ok, baby? Did anything happen to you?"

She touched the boy's hand, but he retrieved it fast, as if he had been burnt. He didn't reply to Kate's questions, focusing his gaze on the ground.

"Aidan?" Castle called him. "Are you ok, bud?"

It was all it took to break the dam. The child's eyes filled with tears and he started shaking. He was quiet, though, keeping the anguish inside.

"Oh, damn." Castle mumbled, picking up his son and cradling him against his chest.

He and Kate looked at each other completely stunned, not knowing what to do or what to say to the little boy crying silently in his father's arms.

* * *

><p><strong>So? Thoughts? Opinions? Death threats? At this stage, anything would be good ;) Thanks for reading!<strong>

Thanks to Tshlw for being the best cheerleader ever and for checking this out for me. All the hugs!


	2. Chapter 2

**A/N:** Hi, fellas! I am sorry this took so long. I am crazy busy at work and to be honest, writing is being a little too hard for me lately. I'm coming from a very long period without writing at all, so be patient, pretty please?

Also, I know this story is supposed to happen around Christmas time, so if it happens to end when it's almost Easter time IRL (hopefully not), or whatever, just deal with me. I am always late for eveything :P

I want to thank you all for being so supportive and for all the nice reviews you left for me and all the follows and favorites. It means the world to me and I am forever grateful.

Thanks to the amazing Tshlw for being the best in the whole world and editing this for me. Any mistake is all mine.

Here's the chapeter, now. ENJOY!

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><p><span><strong>Chapter 2<strong>

Aidan had calmed down by the time they got to the loft, but he had been strangely quiet and somber all the way there.

He never let go of his dad's hand and kept pulling him away from Kate by forcing Castle to run and pick him up whenever the writer tried to wrap his free arm around his fiancée.

Kate didn't know what to do. She had literally no idea of what had happened to the boy that had made him so mad at her when she hadn't seen him since the morning and then he had been the sweet little boy he always was.

Once they arrived at the loft, and after putting away their coats, Kate headed to the master bedroom to get into comfy clothes. Castle stayed behind turning on the TV and setting Aidan on the couch watching his favorite cartoons until they got his bath ready. Then, he disappeared into the bedroom too.

When he entered the room he found Kate sitting on the bed, her head resting on her hands. He could tell that Aidan's strange behavior was really getting to her.

"Hey." He tried to gain her attention, but she didn't look up.

He sat down beside her and stroked the top of her head, then pulled her closer to him, circling his arm around her shoulders. "Come on, Kate. It's just a temper tantrum. It'll be ok."

She raised her head from her hands and he could tell that she was on the verge of tears. "Will it?" She whimpered. "He's never been like this with me before. I don't even know what I have done for him to be so disgruntled."

"Well… Adaptation is hard, Kate." Castle tried to reassure her.

"Adaptation? He's lived here with us for over a year. Isn't it a bit late for that?"

Castle shrugged and hugged her closer. "I have no idea. This is my first time going through this. I guess we're all rookies here." He smiled. "Alexis was with me since birth, so she didn't have much of a choice. By the time she was three I had already gained her little heart with the millions of toys I bought her and the unbreakable rule of having ice cream for dinner every night."

Kate laughed at that and reached for his free hand that was resting on her thigh. "I'm sure that helped, Castle, but I know that is not why Alexis adores you. You are a wonderful dad."

The writer smiled sweetly at her. "Thank you. So are you." At the funny look that remark gained him, he kept talking. "You are an amazing mother, Kate. Seriously. I would never have thought to find myself in this situation. _Ever. _But it happened and to be honest, the way you reacted to all of it really surprised me. You have no idea how thankful I am to have you by my side."

Kate's eyes became glassy again and he smiled and kissed the top of her head, pressing his cheek against it. "You've been amazing with Aidan from the beginning; even when we didn't know if he was mine for sure. He loves you, Kate, and whatever it is that is bothering him right now, it will pass. Everything will be fine again."

Kate gave him a tight smile that didn't make it to her eyes, but she wanted to reassure him, even if she was worried, not only about Aidan's huff, but also about how would the boy react when she dropped the bomb about her pregnancy.

With a last kiss to the top of her head, Castle stood up and offered her his hand to help her get up. "Come on, I have an idea."

She took his hand, but couldn't help narrowing her eyes at him, fearing what his little brain had come up with. "Do I want to know what it is?" She questioned.

"You do." Castle laughed. "So. How about I start dinner and you go give Aidan his bath?" That granted him a quirked eyebrow, but she didn't talk. "You know how much he loves bath time."

Kate smiled. "Castle. He loves bath time because it is 'daddy and Aidan' bonding time. He loves playing with you and listen to all the fun pirate stories you make up for him. I don't think me taking that away will solve anything."

"But we can make it be 'mommy and Aidan' bonding time. Just this once." He countered, tilting his head to the side and squeezing the hand he was still holding.

The cop silently lamented that the _mommy_ part wasn't exactly accurate; that as much as she wanted to be Aidan's mother, that was not the case yet. But it would be. Some day.

"Come on. It'll be fun!" her fiancé insisted, pulling her forwards. "You'll see."

* * *

><p>The bubbles were starting to form in the half empty tub and she checked the temperature of the water for the tenth time, making sure she was not going to scald the boy when she put him in there.<p>

She wasn't used to doing this. Bath time was always Castle's duty. He was the one who was always home to do it and to the boy's delight, his daddy made bath time a real adventure.

She was normally the killjoy; scolding big Castle for making baby Castle too hyper right before his bed time, or giving them both a glare for splashing water on the floor.

Yeah. She was not the fun parent, but she could at least try.

"Okay." She mumbled to herself. "Let's do this."

She went down the stairs to the living area to get Aidan, who was still entranced in his cartoons, all huddled up on the couch.

"Hey, munchkin. Your bath is ready." She called a little bit uncertain of how this would go. "The sooner you get in, the more time you can play with your water toys."

Aidan turned to look at her, his face completely blank. He seemed to stop to think about it for a second, but he didn't move from the couch and, after a few seconds, he returned his full attention to the TV.

Both Castle and Beckett looked at each other in surprise. This for sure was not the usual behavior of their little boy. What the hell was going on with him?

"Aidan." Castle called from the kitchen, his stern tone making the child look in his direction immediately. "Go take you bath, buddy."

The use of the pet name didn't tarnish the intent of his father's order, so the boy hopped down off the couch and followed Kate upstairs, his hands in tight, little fists and tears threatening to fall out of his deep, blue eyes.

* * *

><p>"I don't want a bath!" Aidan screamed for the third time. "I wanna watch cartoons!"<p>

Kate sighed and ran a trembling hand through her hair. She had no idea what to do.

Normally, when the boy got into this level of distress, she was the one to make it better. She was the person Castle went to when Aidan was too stubborn, or was acting up. But this time… This time she was absolutely clueless because, whatever the problem was, she was part of it.

"Ok, Aidan, you need to take your clothes off and get in the tub. You already skipped bath time last night because you fell asleep on the couch." She pointed. "Come on, I'll help you."

The moment she reached for him, the boy stepped backwards, flinching when her hand brushed his wrist. "NO!"

"Aidan! Come on." She chided.

"NO! NO! NO!" The boy cried. "I DON'T WANNA!"

"I know you don't want to. But you have to." She sighed, feeling like she was running out of energy. "If you keep acting like a baby, you're going to bed without dinner."

Aidan frowned at her threat, but he just tightened his fists and screamed. "NO! DADDYYYYY! I want daddy!"

Kate froze. What was she doing so wrong? She just needed him to calm down and do what he was told. It was as simple as that. She had managed to _'tame'_ him a million times. Why wasn't it working now?

She reached for the boy, who had nowhere to go, since he was practically cornered against the wall after his previous retreat, and grabbed his shoulders, softly but firmly, then called his name until he looked back at her.

"Aidan, listen to me. I just need you to take off your clothes and get in the tub, ok? That's all you have to do. Please."

He did nothing. His gaze was lost somewhere above her shoulder and his lower lip was pouting out, making him look absolutely miserable.

And she had caused that.

How was she going to bring another child into the world, when she was incapable of dealing with the one they already had?

The tears that had been pooling in Aidan's eyes started to fall down his little face, making Kate's hear break. She couldn't see him like this. It made her want to pull him into her arms and never, ever let go of him.

And that's what she tried to do; but it was definitely a bad move.

The child jerked away from her when she tried to pull him closer, shoving her arms away from him and making her lose her balance, which resulted in her falling on her butt with a loud thump.

She couldn't keep the hurt away when she looked up at the boy. This was getting way out of hand. "Aidan!" She mumbled, almost inaudibly.

The boy just looked at her, his eyes wide as saucers, and then ran out of the bathroom crying for his father.

* * *

><p>When Castle walked into the bathroom with Aidan perched on his hip, she was still trying to get up from the floor.<p>

"What is going on here?" Rick asked, completely lost. "What are you doing there?"

"Taking a nap." She snapped, but then closed her eyes hard and, after a few seconds and a couple of deep breaths, she looked up at him apologetically, stretching her arm towards him. "Care to help me up?"

The writer put the boy down and reached for her immediately. "Oh. Sure." He grumbled. "What happened?"

"I… fell." She lied, rubbing her left elbow.

Castle narrowed his eyes and nodded. "Uh huh. And why was this little man screaming like he was being followed by an army of ghosts?" He inquired, turning his gaze towards Aidan, who was busy examining his naked feet. "Hmm?"

The boy shrugged, but didn't look up at his father.

"He doesn't want to take a bath." Kate supplied. "He doesn't let me even touch him, Castle." She almost sobbed. "I don't know what to do."

Rick sighed loudly and crouched in front of his son. "Ok, buddy. What's going on? You know you have to take your bath."

He only got a deeper frown from the child. "I know it's normally me who plays with you during bath time, but I am busy making dinner. Can't you be nice to Kate and help her a little bit? You guys can have fun together too."

"NO! She can go make dinner."

Castle huffed out his frustration and moved closer to the boy. "What's wrong with Kate, Aidan?" The writer questioned. "What's happened to make you so mad at her?"

Nothing. He didn't get any kind of response from the kid. Just his eyes locked to the ground and the pout of his lips.

"Baby, did I do anything that bothered you? You know you can tell me." Kate intervened, trying futilely to make the boy react.

"Aidan. You need to tell us what's wrong, buddy. You can't keep being mean to Kate. Kids are supposed to be nice to their mommies." Castle reprimanded.

At that, Aidan raised his gaze from the floor and looked at his father with a broken expression, letting the tears fall down his face again. "SHE'S NOT MY MOMMY!" He yelled, and then stormed to his room, closing the door behind him.

* * *

><p>Castle stood in the middle of the hallway, looking between Aidan's bedroom door and the stairs Kate had sneaked away through when he tried to follow his son.<p>

He had no idea what to do. He more than anything wanted to help, but the way to do it, totally escaped his mind.

It pained him to no end that two of the most important people in his life were unhappy and obviously suffering. He was at a loss about what was going on with Aidan, and until the boy didn't open up and talked about it, there was not much to do, so he decided to go comfort Kate and let Aidan simmer down before trying to talk to him again.

With a deep sigh, he walked down the stairs and to his bedroom, where he found Kate with her face sunken in her pillow.

"Hey." He practically whispered, not wanting to startle her. "Kate, it's going to be ok."

The detective sniffled and buried her face even deeper in the pillow. "You don't know that." Her muffled voice came out. "You heard him." She added, turning to face him at last. "I am not his mommy."

"That never mattered before. And it won't matter again after he comes out of his funk." Castle reassured her, sitting on the bed by her side. "You guys love each other madly. And moms and kids fight all the time. It's natural."

Kate rolled her eyes at that and grabbed a tissue from the box on her nightstand. "I thought that started once they were teenagers. He's four, Castle! He should be wanting snuggles and bed time stories, not worrying about who is or is not his mother."

"You are right, but what do you suggest we do? As you just said, he's only four. It's very hard to explain the situation to a kid that young."

The detective bit her lower lip and grabbed her fiancé's hand, squeezing lightly. "I can't wait anymore, Rick. We have to do it. The sooner the better."

Castle's eyes opened wide, his eyebrows shooting upwards, causing his forehead to crease. "You mean…"

"Yes." Kate proclaimed. "I don't want to wait until after the wedding."

"Ok." The writer nodded. "If that's what you want. I will call my lawyer first thing in the morning."

TBC.

* * *

><p><strong>Dun dun duuuun... Not a really huge cliffhanger, but well. It works haha<strong>

**I hope you enjoyed the chapter. If you did, please let me know. If you didn't, please tell me why and what can I improve about it.**

**Thanks for reading and have a wonderful day/night.**


	3. Chapter 3

**A/N:** Hola! I hope you're all doing great, guys. Here's the next chap to this story. I am hoping to be done with another one and maybe a short epilogue after that. I might be able to finish this before Easter after all. YAY! :P

Thank you so much for your support. I really love reading your reviews, and every email I get, notifying a follow or a favorite, brings a smile to my face. You guys are awesome :)

Big shout out to my lovely Tshlw. I wouldn't be able to write a word without her. She's my best cheerleader/editor/bff. You are worth your weight in gold, girl.

Enjoy the chapter!

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><p><span><strong>Chapter 3<strong>

First thing in the morning, while Kate was getting ready for work, Castle called Robbie, his lawyer.

He and Kate had discussed the possibility of her adopting Aidan legally soon after Castle got total custody of the child. She had been eager to do it from the very beginning, but the more they talked about it, the more doubts they came up with, due to the feeling that the events in Aidan's life were still very recent.

They both knew the boy was mad about Kate. He had been since minute one, but he had lost his mother and found out that he had a father he didn't know existed just a few months back, and that made them think that maybe it'd be better if they waited a bit longer to add a new factor to that equation.

Then, their engagement happened. Aidan seemed to be doing ok after his mom's death almost a year before, and was completely integrated in his new family, so, since they were going to take their relationship one step forward, it only seemed right to do the same with their son.

They wanted to tie the knot as a couple and as a family.

Castle called his lawyer back then, but once they had talked, the writer explained to Kate that the process would be a thousand times easier once they were officially married.

It took Kate a while to agree, but in the end they decided that if being married would speed the process in the end, they could wait a bit longer. They already were a family, with or without the papers to testify to it.

And that had been their plan… until now.

Castle understood Kate's worries about his son's behavior, and he was more than willing to start the adoption process for her. There was nothing he wanted more in the world – aside of getting married to her - but he didn't understand the sudden rush to do it.

After hanging up with his lawyer, he walked back into their room to find Kate sitting on their bed, buttoning up her shirt cuffs with a lost gaze.

"Hey." He muttered to make himself present. "I just hung up with Robbie."

Kate looked up, the tiredness on her face evident even under the thick layer of her make up. "Oh. What did he say?"

"Well…He was surprised. We had already agreed to wait until after the wedding."

Kate huffed a little annoyed. "People change their minds. And we don't even have a date for the wedding yet, Castle. We don't know how long that could be."

"I know." He rubbed his forehead and sat beside her on the bed. "He's meeting us today at 1 pm, if that's ok with you?"

Kate nodded absentmindedly. "Yeah. That's fine. I'll be there."

"Ok. Good."

After an awkward few seconds, he grabbed her hand and tugged at it for her to look at him. "Can I ask you something?"

Kate nodded once and tightened the grasp on his hand. "Sure."

"Um… I know… Please, don't get me wrong, ok?" He pleaded. "I know all this thing with Aidan is really getting to you; I totally understand, seriously. If it was me in your position, I'd be going crazy by now." He joked, trying to lighten the mood. "What I mean is… Why now? What's changed for you to want to do it all so suddenly?" He paused for a second to clear his mind and then added, "You know this won't change things with Aidan, right? He doesn't understand what the adoption papers will mean; how they will change your legal relationship."

Kate scoffed and took her hand away. "This is not about Aidan, Rick. I know he won't care about that bureaucracy. This is about me. I want to be his mother and I don't see the sense in waiting any longer." She reasoned, looking outraged.

Castle nodded, but he wasn't able to reply before Kate started speaking again.

"Remember that time when Aidan was sent to the ER from school?"

He assented, his eyes locked with hers. "Yes. That's when he got his appendix taken out."

"Uh huh. Well… That day I had to take out my badge so the nurse would let me in to see him." She admitted looking up at him under her thick eyelashes.

"WHAT!" Castle squeaked; his brow furrowed. "You never told me that." How could she hide something like that from him?

"Castle, you were worried sick about your son going through surgery. Me having to show off my badge didn't seem exactly important at the moment."

"Yeah." He sighed. "I guess. But after… You could have told me."

Kate sighed loudly. "The thing is that I don't want that to happen again. I don't want to have to flash my badge at a nurse just to be allowed to see my baby when he's sick and alone, laying on a hospital bed." She took a deep breath and pursed her lips, reaching for his hand again. "Maybe you're right and this thing with Aidan has speeded things up. Hearing him say I'm not his mother last night… That was hard, you know?"

"I know, Kate, and I'm sorry if I made you feel like you had to justify yourself. I understand your point, it was just a bit sudden after we decided to wait, but seriously, there is nothing I want more than you to become Aidan's mother for real."

She gave him a broad smile and squeezed his hand. "Thank you, babe. You know I love that kid more than anything in the world."

Castle smiled at that and pulled her closer for a sideways hug, pressing a kiss to her temple as soon as she was close enough.

"So… Um. You love him more than you love me?" He asked wrinkling his nose, oozing mischief.

Kate chuckled and pecked him on the lips before tweaking his ear. "They're two different kinds of love, you lovely idiot." She laughed. "Now, come on. I'm gonna be late for work."

* * *

><p>They spent over an hour at the lawyer's office that afternoon, going through paperwork and discussing how the process would be.<p>

Since Castle was Aidan's father and he was willingly authorizing Kate for the adoption, the requirements were not going to be as exhaustive as you would expect them to be.

Robbie warned Kate about the interviews and how she could expect to be grilled about her lifestyle, the way her getting hurt at work would affect the child, or how she dealt with her gun at home.

Those would be the rougher patches along the way. The actual hard part, which was the adaptation process for the child to get integrated into the new family, was something they wouldn't have to deal with again, so the lawyer didn't see any kind of impediment for Kate to be granted the shared custody of Aidan.

* * *

><p>Feeling, at the least, a little bit relieved, Kate pushed the lobby door open and stepped outside, breathing in deeply. Castle was right behind her and winded a reassuring arm around her waist as soon as they set a foot on the street.<p>

"This is looking good." He mumbled against her temple, leaving a soft kiss there.

Kate smiled and leaned into his warmth. "Yeah. I can't wait for it to be done."

"I know." He sighed. "Want me to walk you back to the precinct?"

Kate smirked and leaned in to kiss his lips softly. "Actually, that won't be necessary. I took the rest of the day off." She grinned. "Since I have to work tomorrow and will be missing our Christmas Eve dinner, I thought it'd be nice to spend today with you, guys. I might even try talking to the munchkin. See if he gives something up about why he's so mad at me."

Castle beamed at her and set them into motion. "That's a great idea, love. I'm sure he'll open up soon."

He was worried about the situation with Aidan, but he couldn't help but feeling excited about Kate embracing the idea of a family Christmas. The previous year had been pretty hard for all of them…

Aidan was still recovering from losing his mother and had only been in the family for a few short months. He was mostly ok, but he obviously missed his mommy very much and couldn't help asking about her every now and again, causing everyone to hurt for him immensely.

And Beckett… Well, her dislike for the season was pretty much known by everyone in the Castle household, so when she announced that she was not going to be there for the celebrations, it was not exactly a shock for anybody, except Aidan who didn't take it well.

So seeing how things were and hating having to spend such important days away from his girlfriend, Castle's brain turned into gear and he decided that, if Kate wasn't coming home for Christmas, Christmas would have to go to Kate.

The whole family spent that night at the precinct, eating among all the detectives and officers working the night shift, singing Christmas carols and opening little gifts Castle had managed to get for every single one of them.

It was a magical night and Kate thanked him for it in several ways, one of them being a promise to be with them for Christmas the next year, which she was actually going to do after her shift on Christmas Eve.

* * *

><p>When they arrived home, they found Martha sitting on the couch reading a script while she watched Aidan as he played with what seemed to be the entire LEGO factory.<p>

The little tiles were spread all over the place forming colorful piles, towers and some pretty impressive walls.

"Hey bug!" Castle greeted kneeling down beside his son. "You building a fort here?"

Aidan nodded but never looked back at his dad, completely focused on his task.

"Can I join you?" The writer tried again, a little concerned about the boy ignoring him. Normally, he was all over him (and Kate) when they got back from anywhere he wasn't allowed to accompany them to.

The kid shook his head and kept on playing, not raising his eyes from his newest construction.

"O-kay…" Castle mumbled, getting up from the floor and wincing at both his mother and his fiancée. "Looks like he's mad at me now."

Martha hummed and nodded, passing another page on the script she was reading. "He must be mad at everybody today. He hasn't spoken a word to me all morning and he didn't want to kiss Alexis goodbye when she left for her study group earlier."

"Well, that's weird." Castle observed. "He's never done this before. I don't get it."

Kate sighed and left herself fall onto one of the kitchen stools, feeling completely defeated. "This is all my fault. He's mad at me and I don't even know wh-…" She gasped midsentence when realization hit her. "Oh, crap."

"What?" Castle asked intrigued. "What is it? You ok?"

Kate nodded dumbly and bit her lip. "Yeah. I just… I remembered something."

Rick's eyebrows raised in amusement. "You remembered what exactly?" The writer inquired, his curiosity growing.

"I'd rather talk to Aidan first. Alone." She remarked, raising from the stool and heading to the bedroom to get changed. "I think I know how to fix this."

* * *

><p>With Martha having left for her studio, for a rehearsal with her students, and Castle at the store, getting some groceries for the Christmas Eve dinner, Kate was left alone at the loft with Aidan.<p>

Her fiancé had been very reluctant to leave the two of them alone after the previous night's incident, but she had managed to persuade him, even though he had been extremely curious about what she was going to talk to the boy about. Nothing she hadn't been able to placate with a soft kiss and a "_trust me, Castle_" as she pushed him out the door.

Now, she was perched at the office door, watching Aidan play with his colorful sea of Legos, building taller and taller walls around him, like a painful metaphor.

Taking a deep breath she started pacing to the kitchen, trying not to pay attention to the boy as she passed beside him. She wanted to give him space until she found a way to approach him.

She grabbed a bunch of ingredients from the pantry and set up camp on the counter, to start mixing the batter for her favorite gingerbread cookies. It was her mom's recipe and she hadn't made them in a while, but they were delicious and if her plan didn't go well, at least she would have something to nibble on while she drowned her pain in hot chocolate.

The batter was ready and she put it to chill in the fridge. It would still take a while for it to be ready for rolling, so she decided to sit in the living room with Aidan.

The boy was now playing with his hot wheels, rolling them inside the impressive wall he had built around himself, making gear noises that made him purse his lips in an extremely cute pout.

"Hey, bug. I am making cookies." She started, her tone as friendly as she could manage. "Would you like to help me decorate them later?"

She got no response, which didn't surprise her at all. There had to be a way to make him talk.

"Aidan? Did you hear me?" She asked, slipping down from the couch to the floor and sitting crossed legged right beside the tile fort. "Can you talk to me? Please?"

The boy stopped playing with his car, inhaled deeply and simply shook his head.

"_O-kay._" She whispered to herself. "So you won't tell me why you are so mad at me?"

"No." The boy barked, surprising her with the harshness of his voice. "Go away."

Kate's heart broke at his words, but she didn't move. She had told Castle that she would fix this mess and she would. She had to gain her little boy back.

"I am not going anywhere, Aidan." She vowed. "Please, tell me what's wrong, baby."

The kid dropped his red car and turned to face her with two fat tears rolling down his face. "I'm not your baby!" He yelled, trying to escape from inside the Lego fort he had created and tripping over, falling face first into Kate's open arms.

The kid squirmed and tried to throw off her arms, but she held him tight against her chest. "Of course you are my baby, Aidan. You will always be."

"No." He sobbed against her neck. "You are having another one and you won't want me anymore."

Ah, there it was. Exactly what she suspected. He heard her talking to Lanie and her stupid doubts about having two kids to take care of had resulted in this nonsensical and painful misunderstanding.

It still escaped her mind how it had taken her almost two days to realize what was going on. How could she call herself a detective? It had been so obvious.

"Shh. Aw, sweetie. Of course I want you." She whispered in his ear, cradling him softly to calm him down. "No matter how many babies I have, I will always love you, Aidan."

"But you said you didn't want two babies. You said it was too much."

Damn her stupid mouth! How could she even think something like that?

She exhaled loudly and brushed a hand through Aidan's hair. "I know I said a lot of silly things the other day, baby, but I was scared, you know? Like when you have those ugly nightmares."

The boy raised his eyes and looked at her with a hurt glare. Ok, not the best choice of words. "What I mean is that I felt a little lost and afraid and sometimes when one is feeling that way, they say some stupid stuff."

"Stupid is a bad word." The boy sniffled. "You owe daddy a dollar."

Kate couldn't help but laugh at the kid's remark. "Yes, I do." She chuckled. "Now, can you tell me why you got so mad at me? I understand you were scared too?"

She questioned, her hand never leaving the soft strands of hair in the boy's crown.

He nodded and snuggled closer to her, causing a soft smile to bloom on her face.

"Aidan, I want you to know something. Look at me, babe." She commanded, tilting his face so he would meet her eyes. "I love you more than anything in the world and that will _never_ change, you hear me? _Ever."_

"Even when you have the new baby?" He asked, his lower lip pouting out.

"Even then. And the new baby will love you so much too. You know why?"

Aidan shook his head and sniffled. "Why?"

"Because when that baby comes, you will become its big brother and he or she will be _so_ proud of you, Aidan. You will be their hero." Kate explained, smiling at the kid's awed expression. "You will get to teach them how to play, how to trick mom and dad, how to get into our bed without being noticed…" She joked. "You guys will have so much fun together."

"Will he play laser tag with me and daddy and Lexi?" He asked completely thrilled.

"Sure!" Kate assented. "But… we don't know if it'll be a boy yet, hon."

"But I already have Lexi! Can we take it back if it's another girl?"

The detective tried to hold back the fit of laughter that she felt coming at the boy's question, but she barely managed to do it. "Um… I am afraid not, bug. But girls can be pretty fun too, you know." She reassured, stroking his back. "You love playing with your sister."

"Yeah." Aidan agreed. "But a boy would be way cooler."

Kate snorted and kissed the top of the kid's head, pulling him closer to her and savoring the first moment of peace in the last 24 hours.

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><p><strong>Thank you, thank you, thank you so much for reading. I hope you guys are enjoying the journey as much as I am. <strong>

**Please leave a comment below so I know what you liked the most; or the less. What would you do after this? How would you think Kate should tell Castle about the baby? I would love to know what you think.**

**Until next time! xoxo**


	4. Chapter 4

**A/N: **Hey, guys! Yeah, I know. It's been almost 3 weeks, but they've been very eventful 3 weeks. You guys know how life can be a bitch sometimes, and adding that to my chronic lazyness is not helpful at all.

Anyway, this is the last chapter to this story. I will be **hopefully** posting a short epilogue soon. Won't give you a date cause I would surely miss it.

You guys have been great with your reviews and follows and all that. I am sorry I haven't been replying lately, but yeah, life again. I will try to get back to all of you as soon as I can. You rock and make all the writer's block and frustration worthwhile. Thank you.

ENJOY!

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><p><span><strong>Chapter 4<strong>

When Castle arrived at the loft, he found his son and fiancée working in the kitchen in apparent harmony. Kate was rolling what appeared to be cookie dough on the counter and Aidan was holding a bell cookie cutter, looking as the detective worked, and eager to start with his assigned job of cutting the delicious forms.

He smiled as he approached them and left the paper bags on the counter next to the fridge.

"Hey." He greeted. "I see you worked out your differences." He muttered in Kate's ear, as he reached to ruffle the boy's hair. Then, he leaned into his girlfriend's space and stole a kiss from her lips, making her chuckle. "Hi gorgeous."

"Hi handsome." She laughed against his lips. "We worked it out." She offered. "And now we're going to celebrate by eating ourselves into a sugar coma. What do you say? Want to join us?"

"Sure!" He replied, his face brightening at the prospect of spending the evening decorating and eating Christmas cookies. "Just let me get changed and I'll be right back."

Once the writer disappeared into their bedroom, Kate turned her attention to Aidan, who was playing with some of the leftover batter as if it were some kind of sticky play dough.

"Hey, munchkin. You remember you can't tell daddy about the baby, right?" She reminded him. "We will tell him tomorrow night when I get back from work."

"It will be daddy's first Christmas present." The kid chimed in. "I know."

"Exactly." Kate smirked. "You will be my little elf." She added, winking conspiratorially at the boy. "You sure you'll be able to wait up for me? It might be way past your bedtime when I get home."

"I will wait. I have a plan." He whispered, asking her to come closer by wiggling his little finger. "I'm going to stay up to see Santa." He confessed. "My friend Jamie said he saw him leaving his presents last year and I want to see him too."

"Ooh." The detective nodded amused. "I see. Well, good luck, honey."

Kate smirked as she started transferring the already cut cookies onto a baking sheet, so she could put them in the oven when they took out their first batch. She placed the pan on the other end of the counter and turned to the boy again, her hands at her hips.

"Ok, scullion. Time to cut more cookies. Choose a shape."

Aidan checked all the different cookie cutters they had scattered on the kitchen island, tapping his index finger against his chin in thought, completely undecided.

"We already have gingerbread men and bells." Kate prompted. "Now what?"

"Um… Reindeers!" He exclaimed, picking said cutter from the counter. "We can paint their noses red, so they look like Rudolf."

"Did I hear Rudolf cookies?" Castle asked, walking out of his office, zipping up his worn out, blue hoodie. "Those are my favorite!"

"We're giving them red noses and all, daddy. Wanna help?"

"Of course, buddy. What do I do?" He asked, stepping next to his son and looking at Kate.

The detective helped Aidan finish cutting the shapes and handed Castle a pair of oven mittens. "For now, you can take out our first batch" She ordered, winking at him and patting his ass when he walked by her. "Then you can help me roll out more dough."

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><p>An hour and a half later, the three of them were sitting at the dinner table, each with a tube of glaze in hand, decorating dozens of delicious cookies.<p>

Aidan was completely entranced by the activity,

"Wow, look at that Rudolf!" Castle praised, his boy. "You're a little artist, but you need to put the frosting on the cookies, son, not on you." He reached for the boy's head and brushed some yellow glaze away, picking up some of it and putting it in his mouth. "Yummy."

Aidan smiled broadly at him and pointed at his father's cookie bells. "That one looks funny, daddy." The boy said, his face breaking into a grin.

Kate laughed and picked up the aforementioned cookie, to take a closer look at it. "Yeah, Castle. We're making jingle bells, not high as heck bells." She joked.

Aidan looked at her a little confused about her comment, but smiled, turning to his dad with a solemn look. "Daddy, bells don't have eyes."

"They don't?!" The writer exclaimed in mock surprise. "You can't be serious."

"They don't!" The boy insisted. "But I like yours. They're cool."

Castle's face softened at his son's words, turning into a smug grin mere seconds later when he turned to look at his fiancée. "Ha! See? My bells are cool. Aidan said so."

"Mhm." She just replied, pasting a candy button on her last gingerbread man. "What about my little men, huh? Aren't they cool too?"

Aidan stretched his neck to look at Kate's cookies that were lining up, painting a colorful parade on the table. "Yeah. You made Santa!" The boy said; picking the cookie up and biting its head off.

Both adults laughed at the kid's antics, looking at each other with a stupid and proud grin on their faces before going back to their task.

Kate sighed, picking up a plain gingerbread man and a tube of red frosting. "I guess I'll have to make a new Santa."

* * *

><p>They put the boy to bed at 9 pm. He had fallen asleep snuggled between the two of them, his head on Kate's chest, while they watched his favorite movie in the world. <em>Cars 2<em>. He was obsessed with it and it was always his choice for movie night. They had watched it so many times that every single member of the family, including Lanie and the boys, could quote the whole thing from start to end.

After cleaning up the kitchen and putting away all the cookies into containers and little plastic baggies to give away to friends and family, they retired to their bedroom for the night.

It was then, when they were both sitting in bed side by side and alone, that Castle asked the feared question.

"So, what was the problem? Did he tell you why he was so mad?"

Kate took a big gulp of air and bit her lip, trying to come up with a good answer so he would stop digging for more. "Um… yeah, but it was all a misunderstanding." She explained vaguely, turning the page of the book she was pretending to read.

Castle frowned. "A misunderstanding about what?" He asked again.

She sighed. She should know by now that her fiancé was too curious to stop at the first question. "Just something I told Lanie on the phone."

"Yeah, but about what? What were you talking to her about?" He inquired, his curiosity growing even more at her reluctance to talk about it.

Kate rolled her eyes and closed her book. "It was nothing, Castle."

"Then why don't you want to tell me about it, _Kate_?" He was amused by it all, she could tell from the tone of his voice. "Come on. I suffered through it too. I deserve to know."

"Okay. I was talking to her about your Christmas present." She blurted, her gaze focused on the duvet. "That's why I didn't want to tell you."

Castle's brow furrowed once again, looking at her with confused blue eyes. "My Christmas present? That's what caused this ordeal? Why?"

Kate shrugged. "He misunderstood my words. That's it."

"I still don't get it. Why would Aidan get mad at you about a gift? It doesn't make any sense."

"Castle, he's a four year old who misunderstood an adult conversation. It's not so hard to understand." She muttered annoyed. If he kept asking, she was going to blurt it out in frustration and she wanted to wait. She wanted to do it right.

"Ok. Fine. Don't tell me." Castle whined.

He was a little irritated by her secrecy, she could tell, but there was nothing she could do about it. "You will find out soon enough, babe. I just don't want to give away anything about your gift. It's a surprise."

"A good surprise?" He winced.

"Rick, it's a gift. How bad do you think it can be?"

* * *

><p>She was nervous. She was so very nervous. She had been fidgety all day, and jumpy too, but this was a very important day for her. For them.<p>

The time had been passing by incredibly slow and work had been unusually boring for Christmas season. The holidays were normally on of the busiest times of the year for them. It seemed that the ever-present joy and happiness made people snap in the worst of ways, but apparently, this year was an exception.

She checked her watch for the thousandth time. It was almost 10 pm. Two more hours and she'd be able to go home to her family and give Castle his little present.

She sighed. She knew he loved kids. Just the way he had reacted when he found out about Aidan was proof of it. He had been thrilled to become a dad again and that had served to reaffirm how much he loved that role.

The truth was, that they had never discussed children beyond the idea of her adopting Aidan. They had never talked about it. Kids had been mentioned once or twice in casual conversations, but it had never gone any farther.

Yet, here she was, four plastic sticks and a blood test later, trying to make her heart go back to a normal rate after thinking about how her fiancé would take the big news.

Maybe her fear was a little bit unfounded, but this was totally new for her. It was true that she had been a mother to Aidan for the last year and a half, and it was true that she loved every little part of it, but even though she was already a mom in practice, the truth was that pregnancy, labor and newborn babies were a completely new world for her.

She was terrified; and as much as she tried to tamper down her apprehension, the feeling was stronger than her will power.

* * *

><p>Midnight arrived faster than she anticipated, given the speed time had been passing by all evening.<p>

When the clock struck twelve, she picked up her bag, put on her coat and wished her colleagues a merry Christmas before heading out for the night.

She had a stop to make before she went home. Having come up with a way to tell Castle about the baby, she needed to buy one last little thing to finish putting her plan together. She really hoped it would work the way she wanted it to.

* * *

><p>When she walked into the loft, she couldn't help but smile at the sight that welcomed her home. She felt like the luckiest woman on Earth.<p>

Martha, Alexis and Castle, were all cuddled up on the couch with a sound asleep Aidan resting in their laps. '_It's a Wonderful Life'_ was on the TV, but all of them looked like they belonged in bed, their faces showing the tiredness and fatigue of the day at such a late hour. Yet, they made such a beautiful picture that she felt her eyes watering. _Stupid hormones_.

Kate walked into the living room area and leaned in to kiss her fiancé on the lips, brushing the sharp angle of his jaw with her thumb. "Hey." she whispered against his skin. "Merry Christmas."

Castle replied in kind, kissing her soundly, before letting go of her so she could say hi to the rest of the family.

Martha and Alexis welcomed her with open arms, both hugging her hard and asking about her day at work. The older woman patted the spot beside her on the couch, silently asking her to sit with them, and she did.

"How was your night, guys?"

"It was good." Alexis replied, her eyes soft and tired. "We missed you, though. The bug's been asking about you every five minutes." She laughed.

Kate smiled and stroked the socked, little foot resting on Martha's lap. "Poor thing. I asked him to wait up for me…" She offered guiltily. "He should have gone to bed hours ago."

"He's fine, Kate." Castle assured her with a tender smile. "It's just one night. We can put him to bed now."

The writer didn't even move an inch when the boy stirred and rubbed his face against his thigh. "Not sleepy." He mumbled, his voice muffled by his father's leg. "I wait for Katie."

The boy's eyes were still closed when he turned his face around, rubbing a hand against one of them.

Kate left her spot on the couch and crouched before Castle to softly caress the kid's face. "Hi, baby. I'm home."

His bright blue eyes opened to her and he grinned. "Katie! Marry Christmas!" He yelled, launching himself into her arms and dropping sloppy kisses on her cheek. "I wait up for you! Can we give daddy his gift now?"

She chuckled when she noticed Castle's surprised expression at his son's words. He sure was intrigued. She could tell. _Good_. He was going to have the surprise of his life.

"Of course, honey. Why don't you go pick yours from the pile? Just _one,_ ok?" She reminded him.

The previous year had been hard to keep him from opening every single package under the tree. Hopefully, this time it would be different, but just in case, Alexis followed the boy to the tree to keep an eye on him.

"Why do we have gifts if Santa hasn't come yet?" The boy asked as he picked one big package with Martha's name on it. "Who brought us these?"

"We did." Alexis explained. "These are our gifts to each other. We'll get Santa's after we go to bed tonight, so you better be good." The young woman admonished with a smirk.

"We leave the heavy lifting to old Saint Nick." Martha chirped, sipping from her glass of red and winking at her son.

"HA! Yeah…" Castle scoffed, earning an elbow to the ribs from Kate.

"Will you shush!"

"Sorry."

The young redhead laughed at her father and then removed their grandma's gift from the boy's hands before offering him one of the smaller boxes with the tag '_Little A' _on it. "Uh, uh. This one's not yours, munchkin."

"But I want the big one!" He whined and reached for the gift, jumping when his sister lifted it over his head. "Gimme."

"That is grams', baby." Kate pointed. "I am sure Santa will bring you big presents tonight."

"But I want them now!"

"Aidan." Castle quarreled. "You heard your sister. If you don't behave Santa's gonna put you on the naughty list."

The boy's eyes went wide and stopped his hopping, raising his hands in surrender. "I am good, daddy. Sorry."

"S'ok, baby. Go open that one." Kate instructed, nodding at the box Alexis was holding now.

The kid did as told and picked up the gift from his sister's hands, tearing off the colorful paper and then stopping short when he saw the picture on the box.

"A phone?" He asked, his brows furrowed and his lower lip pouting out.

Castle laughed as he took out an identical device from a drawer. "Nope." He said, turning the thing on and wincing at the static noise that came out of it. "They're walkie-talkies!"

Aidan smiled, still a little confused and handed his walkie-talkie to his dad so he could turn it on for him. "Cool!"

"Now we can talk when you're upstairs playing in your room." Castle exclaimed, handing the receiver to his son.

The boy's face fell as soon as his father pronounced those words. "I don't like playing in my room. It's scary!" He yelled, dropping the device and latching onto Kate's leg, like he always did when he was upset.

"Bug." The detective called, tapping on his crown. "Come on, baby. Daddy just meant that now you'll be able to talk when you guys are in different rooms. Right?" She prompted, glaring at her fiancé.

"Um, yeah. Of course, buddy." He rushed to reassure the boy. "You don't have to play in your room if you don't want to."

Aidan unstuck his face from Kate's leg and looked up at him. "Really?" He pouted.

"Really."

"Okay."

The boy let go of Kate's leg and grabbed the walkie-talkie from where it had landed on the floor, giving everyone in the room a sly smile.

They really needed to figure out how to deal with his fear of being alone.

Brushing a rebel strand of hair out of the kid's face, Kate cleared her throat and asked, "Ok, who's next?"

"ME!" Castle screeched, reaching out to grab a pretty small box with his name on it.

Kate put a hand to his chest and narrowed her eyes at him, shaking her head and retrieving the box from his hands. "Oh, no. You're going last, mister."

"What? Why?" The writer whined.

Kate smirked mischievously, patting his chest. "Because…" She started, winking at Aidan. "Yours is the most important one."

Martha and Alexis, who had helped her choose the new watch she was supposed to give him, looked at each other more than a little confused making her chuckle.

Oh, yeah. They didn't know either.

* * *

><p>Everyone but Castle had already opened their gifts, and even though she knew how much he loved seeing his family happy and enjoying their Christmas presents, she knew her fiancé was starting to get anxious. He loved surprises more than anybody and she had made him wait long enough.<p>

"Ok, Castle. Your turn." She announced, getting everybody's attention.

The writer reached for the last little box that was left under the tree, but Kate stopped him mid action. "Uh, uh. We'll save that one for later." She ordered, producing a package from behind her. "Open this one first."

She handed the packet to him, but pulled it away right when he was going to grab it. "You will have to share it, though." She added, realizing that the surprise was going to affect every single one of them.

"Oooh." Castle exclaimed. "You got us new laser tag gear?" He asked, eager to get his gift.

Kate chuckled and shook her head. "Uh, nope." She replied. _But I got you a new future player._ She thought to herself, finally handing him the present with a broad smile on her face.

"It must be something really big." Rick laughed. "I know that smile."

She just nodded, nervously biting her lower lip. "Oh, babe. You have _no_ idea."

Once he had the package in his hands he started fondling it and turning it around, trying to figure out what it was, knowing how much it bothered her when he stalled like that.

"Ugh. Castle!" Kate whined. "It'd be nice if you opened it this Christmas."

"Ok. Ok!"

He removed the wrapping paper and pulled out a red, white and green stocking, adorned with little snow flakes and candy canes. It matched the pattern of their family set, but this one had no name on it.

"A stocking?" He asked incredulous. "Um. Thanks. I… uh… I guess mine was getting old."

Kate snorted. "Well, it is not for you, babe. I told you, you would have to share." She reminded him, smiling at his slow nod. "Why don't you look inside?"

"Yeah. Inside, daddy." Aidan cheered.

"You know what this is?" He asked the kid, narrowing his eyes. "You two planned this together, didn't you?"

The boy nodded and gave him a sly grin. "_Inside_, daddy." He insisted.

"Okay. Inside."

He put his hand into the stocking and took out a folded piece of paper and a little plastic bag with a cookie inside.

"Alright, let's see." He mumbled, unfolding the piece of paper. "Um, this is a…" His eyes lifted from the paper and he swallowed. "A medical report."

Kate heard somebody gasp behind her and turned to find Alexis with a hand to her mouth and her eyes wide open. She nodded, knowing the girl had figured out what it was, and then felt her heart melt at the look of pure joy she got in reply.

"There's your name on it, Kate."

"Yeah. I _know._" She mocked. "Keep reading."

"Hemoglobin, hormones levels…" He scanned the document, trying to figure out what made it so important. "Oh, my God." He gasped at last. "Kate?"

The detective nodded, tears starting to gather in her eyes.

"It… It says 'pregnancy: positive' here."

"Uh huh."

"We're… We're pregnant? Oh, God. We're having a baby!" He screamed, passing the piece of paper to his mother, who was already brushing away a traitorous tear. "Oh, Kate." He sighed, pulling her into a tight hug.

"Daddy! You didn't see my gift!" Aidan complained. "I made it."

The writer pulled away from his fiancée and took a look at the little package that he was still holding in his hand. The cookie.

"You made this?" He asked impressed, gazing at the rounded form. It had a smiley face drawn with red frosting on one side and on the other it said '_Castle Baby #3'_ in quirky multicolor letters.

Castle laughed at the inscription and leaned down to pick his son up. "I love it, buddy. Thank you." He whispered against the boy's forehead. "I can't believe you wrote that!"

Aidan blushed. "Katie helped me." He offered. "But I chose the colors."

"Oh. Well done. I love the smiley face too."

The kid beamed at him and hugged him hard. "You know what's the best part?" He asked, his eyes wide. "I am going to be a _big_ brother!"

After having received the customary congratulations from his mother and daughter, Castle hung the new stocking by the fireplace, right beside Aidan's, tugging at the soft fabric as he stepped away and towards his family.

"This is the best Christmas ever." He said, turning around and pulling Kate into his arms once again.

"Wait until next year." She whispered against his skin. "I think it will beat this one by a lot."

Castle could only nod, burying his head in Kate's shoulder. Next year was going to be extraordinary for sure.

THE END

Short epilogue coming soon.

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><p><strong>Thank you so much for joining me on this journey. It has been great having you onboard. Leave a review if you feel like it. I would love to know what you think.<strong>

**Big thank you to my own personal cheer leader, Tshlw. I know I wouldn't have finish this without you nagging me all the time haha. Also thank you for editing and proof reading every time I freaked out. Love you!**


	5. Epilogue

**A/N:** Hey guys! Late as always haha. At least I didn't hint when I was expecting to post this time. Anyway, here's the epilogue to this little story.

Thank you SO very much for all your support and your beautiful words. You've been great to me and I love you all for it.

Until next time! Enjoy :)

* * *

><p><strong><span>Epilogue<span>**

_**One year later. Christmas Morning.**_

"Castle, if you wake up the baby I am going to kill you!" Kate scolded her husband through gritted teeth, trying to balance the mountain of pans she had taken out of the cabinet. "It took me hours to get her to sleep last night."

"I know, Kate." The writer mumbled as he picked up the spatula he had just dropped. "I was there with you the whole time."

The dark circles under his eyes, which matched hers, were the proof to that. It had been a very long night for both of them. Actually, it had been a very long four months.

Beckett looked regretfully at her husband and bit her lower lip, her nose scrunching adorably in the process. "I know, babe. I'm sorry I snapped at you." She apologized, stroking his back softly. "She's just _so_ hard to comfort…"

"I wonder where did she get that…"

"Very funny." She replied, slapping his ass a little bit too hard.

"Ouch! What?" Castle laughed. "She's a tiny Beckett clone after all. Just saying."

Kate laughed and shook her head in amusement, turning to work on the coffee machine.

They had agreed on surprising their family with an opulent Christmas breakfast and, even though they didn't have much rest the night before, thanks to their light sleeper of a daughter. Here they were at 7 in the morning, making Christmas tree shaped pancakes, eggs, bacon and sausages.

Castle flipped the last of the pancakes and poured orange juice into the six glasses he had lined up on the counter; then turned to help his wife with the bacon.

"Mmm. That smells good, Mrs. Castle." He whispered against the shell of her ear. "Can't wait to get a bite."

His teeth pulled on her earlobe as his hands wandered under the hem of her shirt, leaving goosebumps in their wake and making Kate squirm.

She barked his name as a warning, but it was to no avail, when he pressed his body against her back and started nuzzling her neck. "Rick." She sighed, too into it to sound annoyed. "Aidan could come down any minute."

"I am sure we would know if he was awake." He murmured against her skin. "Being quiet is not exactly one of our son's many qualities, Kate."

"I wonder where did he get that." She mocked in reply, slapping his hands off and raising an eyebrow at him when he pouted.

"Your pancakes are burning, you goofball."

"Oh, damn!"

* * *

><p>Their breakfast was ready by 7:30, and they were a little surprised – and disappointed - that not a single member of their family was up yet.<p>

It was Christmas morning; where was everybody?

Placing the last plate on the dinner table, Castle checked his watch again. A quarter to eight.

He could understand that his mother and daughter, and even Beckett's dad were still asleep. It had been a long day for all of them, but what he could not believe was that their five year old was still not in the living room, half way into a sugar overdose and surrounded by mountains of wrapping paper and toys.

"This is weird. Where is Aidan?" The writer muttered, sitting down on one of the chairs. "He should be up by now, he never sleeps this late. Like, _ever_. Not even when he's sick. Remember that time he had the flu and woke us up before 5 am every single morning?"

Kate smiled and nodded, sitting on his lap and stroking the soft locks of hair at his nape. "Yeah, I remember that. Hard to forget when I was eight months pregnant and had to move around with a kid hanging off my neck for a week…"

Castle laughed at the memory of how their son had been so clingy during his sickness. It had been a hard few days, but they held some good memories as well. The second day into it, Aidan had called Kate 'mommy' for the first time since the adoption had been final, and his wife had been so emotional about it, that she kept tearing up every time she as much as thought of it. She still grinned like an idiot every time the boy called her that, which made him fall in love with her a little bit more each time.

Kate nuzzled his neck and pressed a soft kiss there. "Maybe he stayed up late to wait for Santa." She offered. "He didn't get to do it last year."

Castle chuckled. Last Christmas day, they had found the boy asleep when they came out to place the presents under the tree very early in the morning. He had been lying on the couch, facing the tree and covered with his bed comforter. After waiting up for Kate that night, none of them wondered why his plans for catching Santa by surprise had failed.

"True." Castle agreed. "We need to teach him how a stake-out goes." He added, pecking Beckett on the lips. "Too bad he's too young for coffee."

"Too bad?" Kate squeaked. "Thank God! He's hyper enough without the extra caffeine, thank you very much."

A soft whimper coming from the baby monitor that Kate had placed on the kitchen island caught their attention, making both of them smile.

"Well, at least one of our offspring is ready for breakfast." Castle sighed, letting go of his wife and following her upstairs.

"Yeah. Too bad she's only ready for mommy's boobies yet."

"Hey. I'd be perfectly happy if that was the only thing I could eat." The writer chimed, pushing the nursery door open to let his wife in.

"Castle!" Kate hushed.

"What?" He asked amused. "It's true."

"Aww."

The writer stopped in his tracks and frowned at his wife. She had been scandalized just one second ago, what was so- _oh._

"Look at that." Kate whispered; leaning into his side and smiling so broadly he thought her face would split in half.

The scene before them was the sweetest thing he had ever seen. On the rocking chair, beside the crib, was Aidan, asleep and all bundled up in a blanket, his hand reaching through the bars for his sister's who was grasping the boy's index finger, trying to put it in her mouth.

"Isn't that the most beautiful thing you've ever seen?"

Castle smiled and kissed the top of her head, nodding in Aidan's direction. The boy was starting to stir in the chair, his eyes scrunched closed as he yawned loudly.

"Morning, bug." Kate greeted, leaning down to kiss the boy on the forehead, and then crouching in front of him. "Did you sleep here, baby?"

Aidan nodded and reached for Kate, snaking his arms around her neck and letting her pick him up from the chair. "She was scared, mommy." The boy explained. "I took care of her."

"Yes, you did, sweetheart." She agreed, hugging her boy closer and smiling at her husband.

Castle assented. "You are the best big brother ever." He said, ruffling the boy's hair and kissing his shoulder.

"Really?"

"Absolutely!" Kate insisted. "Now, how about we have some breakfast and you open your presents, huh?"

"Yayyyy!"

Kate moved towards the door and winked at her husband, who was already leaning over the crib. "Carry her downstairs for me?"

"Sure." The writer replied, turning to smile down at his daughter. "Morning, Sadie bird." Castle cooed. "Were you trying to eat your brother's finger?"

* * *

><p>Little past 8:30 am, everybody was up, had eaten breakfast and were now completely entranced opening their Christmas presents.<p>

Piles of wrapping paper surrounded the tree. Their family was laughing and cheering Aidan while he tried to ride his shiny new bicycle. While Alexis took pictures, Jim and Martha tried to put the helmet on the boy, who kept moving and squirming in his grandfather's grip.

Rick and Kate observed them from the couch with little Sadie fast asleep in her mother's arms. They both smiled at the picture they made, so happy and comfortable around each other.

Kate sighed loudly as she leaned her head to rest on her husband's shoulder. "I don't know how people do it." She whispered, her finger stroking Sadie's chubby cheek.

"Do what?"

"Get away from this." She simply said.

Castle frowned and leaned away from her, prompting for a more elaborate answer.

"I mean, I've been here with you guys for six months since I started my maternity leave. How am I supposed to go back to work? All I ever want to do now is stay home, cuddle up with my babies and watch Disney movies until we fall asleep. Is that too much to ask for?"

"No, it is not." He agreed. "I understand you, love, but you knew this day was coming." He mumbled against her temple. "You still have two weeks home, though."

Kate huffed. "That is not nearly enough. You get to be here all the time."

That made Castle wince. He knew she didn't mean it as an accusation, but he also knew that, since the day Sadie was born, Kate had become extremely protective and attached to both their kids, and he truly feared the day she had to go back to work.

"You know you could just stay, right?" He asked, his hand wrapping around hers on their daughter's tummy. "If you feel like you don't want to go back, then don't, Kate."

She gave him a watery smile and nodded. "I know, babe. I'm just being emotional. You know how much I love my job. It's just these stupid hormones. They've ruined me."

"I think you're cute when you're emotional." He let out without thinking. The look he got from his wife, made him rephrase his statement. "I… I mean, you're… Let's pretend I didn't say anything, ok?"

Kate rolled her eyes and smirked, her focus returning to their family and their little cyclist, who was now wearing his helmet and opening a new gift.

"Mommy, look!" The kid yelled. "It's the book grandma Jo read to you when you were little. Grandpa asked Santa for it and he brought it to me!"

The boy ran to Kate brandishing the book, almost smacking it into her face when he got close enough to her. "Easy, baby." She laughed. "Let me see."

"_Where The Wild Things Are_." Castle read. "I loved that book as a kid too."

"Really?" Kate and Aidan asked at the same time, making the author smile and nod stupidly.

"Can we read now?" The boy requested. "Grandpa can do it!"

Aidan rushed towards where Jim was and handed him the book, pulling on his sleeve to make him walk faster to the sitting area.

"You read, grandpa."

He climbed onto the couch, right between Kate and Castle and pressed a kiss to one of his sister's feet. The baby was now awake, having finally noticed that something interesting was going on around her. "It's story time, Sadie bird." He whispered. "You listen, ok?"

Everybody in the room smiled at the boy's sweet gesture, and then Jim started to read.

"_The night Max wore his wolf suit and made mischief of one kind…"_

Castle observed his family for just a moment longer, an unstoppable grin growing on his face. He had never been happier than this, and the feeling was so overwhelming that he felt the tears forming in his eyes and constricting his chest.

"You were right." He whispered in his wife's ear.

Kate frowned and turned to look at him at a loss. "About what?"

The writer chuckled and stretched his arm to rest over her shoulders, pulling her closer to him. "This Christmas beats last year's by a lot."

_**THE END.**_

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><p><strong>Thank you so much for reading, everybody. It's been a great ride. Let me know what you think. Your opinions are always appreciated.<br>**

**To tshlw: Thanks again for being an awesome cheerleader and for encouraging me and helping me break my writer's block. You're the best.**


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